`ConstantValue` is the only other ctor allowed when subtracting from slice ctors
`ConstantValue` is the only other ctor allowed when subtracting from slice ctors

aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust